On agricultural tractors and off-road machinery it has been conventional to provide a manually actuated switch for controlling energization of electrically controlled devices such as, for example, a power take off system. Conventionally, such switches have been multi-stable, that is, they remain on when switched to the on position and remain off when switched to the off position. A switch of this type has a disadvantage in that if there should be a loss of power, it will cause re-energization of the controlled device if the switch is in the on position when power is restored.
A further disadvantage occurs when multi-stable switches are used in a computer-controlled system where the computer senses the change of state rather than the state of the switch. In this case the operator must remember to reset the switch, otherwise its physical position will not correspond to the state recognized by the computer.
A problem with both multi-stable switches and momentary switches of the prior art concerns safety. An operator may inadvertently actuate the switch and, depending on the device being controlled, this may create a hazardous condition.